This invention relates to an internal combustion engine of the so-called "torch type", wherein a combustion chamber is composed of a main combustion chamber and a preliminary or sub-combustion chamber equipped with an ignition plug, and both combustion chambers are communicated with each other by way of a through-hole, thereby firing a lean mixture charge in the main combustion chamber by utilizing a flame produced in the sub-combustion chamber, and more particularly to a device for feeding a mixture charge to both combustion chambers.
In an internal combustion engine of the type described, it is imperative to feed a lean mixture charge to the main combustion chamber and a rich mixture charge to the sub-combustion chamber. To this end, hitherto, plural intake systems have been separately provided for use in the main combustion chamber and in the sub-combustion chamber. More specifically, independent intake cylinders are connected to the main combustion chamber and the sub-combustion chamber, respectively. These intake cylinders respectively have a throttle valve and a fuel controlling system, and the throttle valves of respective intake cylinders are interconnected with each other by means of linkage or cam mechanism. As a consequence, the device has been complicated in construction and expensive to manufacture. A mixture charge to be fed to the sub-combustion chamber, in general, requires energy proportional to that of the mixture charge being fed to the main combustion chamber, and a ratio in amount, of air being fed to the main chamber so that of the sub-combustion chamber, as well as a ratio in air-fuel-ratio of mixture charges being fed to the main combustion chamber to that of the sub-combustion chamber should also desirably be maintained in proportion to each other. However, in case a duplex carbureter is adopted for a main combustion chamber, it has been impossible to maintain the air fuel ratios for the main combustion chamber and the sub-combustion chamber in proportional relation.
It is accordingly an object of the present invention to provide an intake system in an internal combustion engine having a main combustion chamber and a preliminary or sub-combustion chamber, which permits to feed a mixture charge both to the main combustion chamber and to the sub-combustion chamber, and which is simple in construction.
It is another object of the present invention to provide an intake system in which mixture charges may be fed to the main combustion chamber and the sub-combustion chamber substantially at a given ratio in its amount, with a given ratio in air-fuel-ratio maintained constant.
To attain the objects of the present invention, there is used an injection carbureter, in which a negative pressure in a venturi portion is detected, to thereby control a fuel pressure as well as control a flow rate of fuel. In order to feed air to the main combustion chamber and the sub-combustion chamber, there are provided a single intake cylinder having a venturi portion which allows the passing of the total amount of air to be fed to both combustion chambers and a throttle valve for controlling the amount of air to be fed thereto; a main intake passage leading from the intake cylinder to the main combustion chamber; and a sub-intake passage stemed from the intake cylinder and leading to the sub-combustion chamber. The total amount of air to be fed to both combustion chambers is controlled by the single throttle valve, while a ratio in amount, of air being fed to the main combustion chamber and the sub-combustion chamber is maintained at a given value which is determined according to resistance imposed on air passing through the main intake passage and the sub-intake passage. To feed fuel to both combustion chambers, there are provided; fuel discharge devices attached to the main intake passage and sub-intake passage, respectively; a fuel pressure controlling device for providing fuel pressure commensurate with a negative pressure in the venturi portion; and main and sub-fuel passages which connect the fuel pressure controlling device to respective fuel discharge devices. A ratio in flow rate, of fuel being introduced into one fuel discharge device and into the other fuel discharge device is maintained at a given value which is determined according to resistance imposed on fuel passing through the main fuel passage and the sub-fuel passage, while a flow rate of fuel in respective fuel passage fluctuates according to a negative pressure in the venturi portion. Thus, the amount of a mixture charge being fed to the main combustion chamber and that of a mixture charge being fed to the sub-combustion chamber are usually maintained in proportion to each other, while a ratio in air-fuel-ratio, of the mixture charge being fed to the main combustion chamber and to the sub-combustion chamber is usually maintained constant. Only the sub-intake passage, fuel discharge device and sub-fuel passage are necessary for feeding a mixture charge to the sub-combustion chamber, so that the intake system of the present invention is extremely simple in construction.
In the preferred embodiments of the present invention, a metering orifice is provided in the sub-intake passage for determining a ratio in amount, of air to be fed to the main combustion chamber and to the sub-combustion chamber to a given value, while metering orifices are provided in the main fuel passage and sub-fuel passage, respectively, for providing a given ratio in amount, of fuel to be introduced to the main intake passage and to the sub-intake passage. The use of the metering orifices make it easy to provide a given ratio in amount, of air being fed to the main combustion chamber and to the sub-combustion chamber, as well as a ratio in amount of fuel being introduced into respective passages.
These and other objects and features of the present invention will be apparent from the ensuring part of the specification in conjunction with the drawings which indicate preferred embodiments of the present invention .